Nicolaus Copernicus was a Polish astronomer monk of the Renaissance who formulated the heliocentric theory of the solar system, conceived in the first instance by Aristarchus of Samos. His book "On the revolutions of the celestial spheres" is usually considered the starting point of modern astronomy, as well as being a key piece in what was called the Scientific Revolution at the time of the Renaissance. Copernicus spent about twenty-five years working on the development of his heliocentric model of the universe. At that time it was difficult for scientists to accept it, since it was a real revolution.
